1. Field of the Invention
This invention relates to a blind, particularly to one having an excellent efficiency and its assembling method.
2. The Prior Arts
Conventional blinds generally include a headrail, a bottomrail, a plurality of ladders and a plurality of lift cords combined between the headrail and the bottomrail, and a plurality of slats deposited in parallel between the headrail and the bottomrail. Each slat is provided with a plurality of holes properly spaced apart in the intermediate portion for the lift cords to pass through to lift up the bottomrail so that all the slats may be lifted up sequentially, and the ladders change the angle of every slat in various degrees so that the light may be adjusted in its strength to pass through every gap between every two slats into a room or totally shut out.
However, the conventional blinds have a common flaw that light may enter a room a little through the gap between every two adjacent slats even if the slats are adjusted in the completely closed condition. Moreover, the lift cords located in the intermediate portion of all the slats may interfere with the changeable angle of each slat and prevent two neighboring slats from closely contacting each other, resulting in a very small gap between every two neighboring slats for light to pass through in a room.
In order to shut out light with comparatively good effect, a U.S. Pat. No. 5,727,613 includes slats bored with no holes for lift cords but with a notch provided at two ends respectively, permitting every two neighboring slats to contact closely and vertically with each other when the blind is closed for shutting out light totally.
The blind disclosed in the U.S. Pat. No. 5,727,613 has the slats possible to move left and right, not restricted as such that the slats may slide out of one side of the blind if the blind is inclined to one side (whether right or left).
Further, U.S. Pat. No. 4,951,729, U.S. Pat. No. 5,386,867 and U.S. Pat. No. 6,792,996 have every slat bored with a hole near an end for a lift cord to pass through for preventing the slats from sliding out of a side of the blind. Besides, when the slats are turned in their angle to let every two neighboring slats to vertically contact with each other, the ends of each slat may hide the hole to reduce the volume of light passing there through, in addition to the function that the slats are prevented from sliding out of either side of the blind.
However, such blinds disclosed in the above three patents have the lift cords for moving up the slats and the bottomrail, and the lift cords generally have a big diameter, with the portion of the lift cords near the slats being not so flexible, so the lift cords pinched between two adjacent slats may hinder those two neighboring slats from closely contacting each other. Therefore, a small gap may result between every two neighboring slats, with the effect of the light prevention limited, and even a slender lift cord cannot completely get rid of this flaw, or support the whole weight of the all slats and the bottomrail owing to its weak strength, in addition to potential harm to a hand in pulling up the slats.
Further, a U.S. Pat. No. 5,582,226 discloses a blind provided with lift cords not passing through slats, but said slats still have a hole at two opposite sides and the ladders are twisted so that the slats may not turn smoothly. Moreover, after the bottomrail is lifted up for some distance, it may clearly interfere smooth turning of the slats.
Other two U.S. Pat. No. 6,729,379 and U.S. Pat. No. 6,854,504 acquired by the applicant of this invention include lift cords, and rings added on the lift cords for fitting around a bar located at two sides of slats, instead of the conventional lift cords. But this kind of lift cords can only apply to soft slats. As to a blind provided with rings and hard slats, as the structure disclosed in a U.S. Pat. No. 6,192,963, despite of the rings affixed on the ladders for the lift cord to pass through, there is still a problem of the slats sliding out of a side of the blind.